Hydrogen generator having a porous electrode plate

ABSTRACT

There is provided a hydrogen generator having a porous electrode plate. The hydrogen generator including: an electrolytic bath having an electrolyte of a predetermined amount filled therein; a cover hermetically covering an open top of the electrolytic bath and having at least one hydrogen outlet; an electrode part fixed to the cover and having a porous structure formed on a body portion thereof to allow the electrolyte of the electrolytic bath to pass freely there through, the body portion of the electrode part immersed in the electrolytic bath; and a power supply supplying current to the electrode part.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority of Korean Patent Application No.2007-07209 filed on Jan. 23, 2007, in the Korean Intellectual PropertyOffice, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a hydrogen generator, and moreparticularly, to a hydrogen generator having a porous electrode plate inwhich an electrode plate in contact with an electrolyte is changed instructure to increase a contact area with the electrolyte, therebygenerating a greater amount of hydrogen.

2. Description of the Related Art

Recent years have seen an increasing use of small-sized electronicdevices such as mobile phones, personal digital assistants (PDAs),digital cameras and laptop computers. Particularly, with the start ofdigital multimedia broadcasting (DMB) for mobile phones, a small-sizedmobile terminal is required to be improved in power capacity.

A lithium-ion secondary battery in current general use has a capacityenabling about two hours of DMB viewing and has been performing better.However, as a more fundamental solution, there has been a growingexpectation for a micro fuel cell reduced in size and capable ofproviding high-capacity power.

In general, the micro fuel cell adopts hydrogen as the most appropriatefuel for realizing high performance. This has led to a need for a devicefor generating hydrogen supplied to the micro fuel cell.

There are two ways to produce this fuel cell. One is a direct methanolmethod in which a hydrocarbon fuel such as methanol is directly suppliedto a fuel electrode. The other is a reformed hydrogen fuel cell (RHFC)method in which hydrogen is extracted from methanol to be injected to afuel electrode.

The RHFC method utilizes hydrogen as a fuel in the same manner as apolymer electrode membrane (PEM) method. Thus, the RHFC has advantagesof high-output, high power capacity attainable per unit volume, and noreactant present other than water. However, the RHFC method requires anadditional reformer to be installed in a system, thus hinderingminiaturization.

Also, the reformer includes a vaporizer vaporizing a hydrocarbon liquidfuel into a gas phase, a reforming unit converting methanol as a fuelinto hydrogen through catalytic reaction at a temperature of 250° C. to350° C., and a CO remover (or CO₂ remover) removing a CO gas (or CO₂gas), i.e., the byproduct accompanying the reforming reaction.

However, the reforming reaction in the reforming unit is an endothermicreaction where a reaction temperature is maintained at 250° C. to 350°C. On the other hand, the reforming reaction in the CO remover is anexothermic reaction in which a reaction temperature is maintained at170° C. to 200° C. Therefore, to attain good reaction efficiency, theRHFC method necessitates an intricate high-temperature system, therebycomplicating a structure of an overall fuel cell device and impedingreduction in manufacturing costs thereof.

Moreover, the RHFC method inevitably entails an additional structure forremoving the CO gas or CO₂ gas, i.e., the byproduct generated during thereforming reaction. This hinders reduction in an overall volume of thedevice and in manufacturing costs.

Meanwhile, as a method for generating hydrogen by electrolysis, as shownin FIG. 1, an electrolyte such as sea water is filled in an electrolyticbath 1 of a predetermined size. In the electrolytic bath 1 are immersedan anode electrode 2 formed of magnesium (Mg) more ionizable thanhydrogen and a cathode electrode 3 formed of iron (Fe). The anodeelectrode 2 and the cathode electrode 3 are fixed to the electrolyticbath 1 and a cover 4 having a hydrogen outlet is provided on theelectrolytic bath 1.

Here, when current is supplied to the anode electrode 2 and the cathodeelectrode 3, respectively, magnesium reacts with water according toequations 1, 2 and 3. In turn, magnesium hydroxide is generated in theelectrolytic bath 1 to generate hydrogen according to equation 4.

Mg→Mg⁺²+2e⁻  Equation 1

2H₂O→2OH⁻+2H⁺  Equation 2

2H⁺+2e⁻→H₂   Equation 3

Mg+2H₂O→Mg(OH)₂+H₂   Equation 4

Also, the magnesium hydroxide obtained by the equations above remain inthe electrolytic bath 1, while the hydrogen is exhausted outward throughthe hydrogen outlet 5 of the cover 4 to be utilized as a fuel.

In FIG. 1, un unillustrated numeral 6 refers to a pump for replenishingthe electrolyte bath 1 with the electrolyte. However, an amount ofhydrogen generated in the electrolytic bath 1 is proportional to acontact area between the electrodes 2 and 3 immersed in the electrolyticbath 1 and the electrolyte of the electrolytic bath 1. Here, the anodeelectrode 2 and the cathode electrode 3 are formed of a square plate anda limited number of electrodes are disposed in the electrolytic bath 1,thereby limitedly increasing the amount of hydrogen generated in theelectrolytic bath 1.

SUMMARY OF THE INVENTION

An aspect of the present invention provides a hydrogen generator havinga porous electrode plate, in which a surface area of an electrode partin contact with an electrolyte within a limited space is increased togenerate a greater amount of hydrogen.

According to an aspect of the present invention, there is provided ahydrogen generator having a porous electrode plate including: anelectrolytic bath having an electrolyte of a predetermined amount filledtherein; a cover hermetically covering an open top of the electrolyticbath and having at least one hydrogen outlet; an electrode part fixed tothe cover and having a porous structure formed on a body portion thereofto allow the electrolyte of the electrolytic bath to pass freelytherethrough, the body portion of the electrode part immersed in theelectrolytic bath; and a power supply supplying current to the electrodepart.

The electrode part may include an anode electrode plate and an anodeelectrode plate, wherein each of the anode and cathode electrode platesincludes: first and second holders each provided on a surface thereofwith a porous part through which the electrolyte passes freely; and aporous body fixedly disposed between the first and second holders.

The porous body may be formed of a conductive metal fiber.

The porous body may include at least two layers of conductive metalfiber having a porosity gradient different from each other.

The porous body may be electrically connected to the power supply.

A sealer may be provided between the electrolytic bath and the cover.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a cross-sectional view illustrating a conventional hydrogengenerator;

FIG. 2 is an exploded perspective view illustrating a hydrogen generatorhaving a porous electrode plate according to an exemplary embodiment ofthe invention;

FIG. 3 is a view illustrating an electrode part employed in a hydrogengenerator having a porous electrode plate according to an exemplaryembodiment of the invention, in which A is an exploded perspective viewand B is an overall configuration view; and

FIG. 4 is a cross-sectional view illustrating a hydrogen generatorhaving a porous electrode plate according to an exemplary embodiment ofthe invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Exemplary embodiments of the present invention will now be described indetail with reference to the accompanying drawings.

FIG. 2 is an exploded perspective view illustrating a hydrogen generatorhaving a porous electrode plate according to an exemplary embodiment ofthe invention. FIG. 3 is a view illustrating an electrode part employedin a hydrogen generator having a porous electrode plate according to anexemplary embodiment of the invention, in which A is an explodedperspective view and B is an overall configuration view. FIG. 4 is across-sectional view illustrating a hydrogen generator having a porouselectrode plate according to an exemplary embodiment of the invention.

As shown in FIGS. 2 to 4, the hydrogen generator 100 of the firstembodiment includes an electrolytic bath 110, a cover 120, an electrodepart 130, and a power supply 140.

The electrolytic bath 110 is formed of a rectangular parallelepiped boxhaving an inner space of a predetermined size to have an electrolyte ofa predetermined amount filled therein.

Here, an electrolyte replenishing line (not shown) equipped with a pumpmay be installed on an outer surface of the electrolytic bath 110 toreplenish the electrolyte.

The cover 120 is a plate-shaped structure attached on the electrolyticbath 110 to hermetically cover an open top of the electrolytic bath 110where the electrolyte is filled.

A plurality of fixing holes 122 are formed in an outer surface of thecover 120 to fix the electrode part 130 including an anode electrodeplate 131 and a cathode electrode plate 132.

Also, at least one hydrogen outlet 124 is formed in the outer surface ofthe cover 120 to exhaust hydrogen generated inside the electrolytic bath110 outward.

A sealer 115 made of e.g., a rubber material is provided between anupper end of the electrolytic bath 110 and the cover 120 to prevent theelectrolyte from leaking from the electrolytic bath 110.

The electrode part 130 is fixed to the cover 120 and has a body portionimmersed in the electrolyte of the electrolytic bath 110. The electrodepart 130 is provided on the body portion thereof with a porous structurethrough which the electrolyte of the electrolytic bath 110 passes freelyto increase a contact area between the electrode part and theelectrolyte. The electrode part 130 may be formed of a porous material.

The electrode part 130 includes the anode electrode plate 131electrically connected to an anode terminal of the power supply 140 anda cathode electrode plate 132 electrically connected to a cathodeterminal of the power supply 140.

Each of the anode and cathode electrode plates 131 and 132 includesfirst and second holders 130 a and 130 b each having a porous part 136formed on a surface of the body portion immersed in the electrolyte ofthe electrolytic bath 110. This allows the electrolyte to pass throughthe porous part 136 freely. Each of the anode and cathode electrodeplates 131 and 132 also includes a porous body 130 b disposed betweenthe first and second holders 130 a and 130 b such that the electrolytepassed through the porous part 136 passes through the porous body 130 bfreely to increase a contact area between the electrode part and theelectrolyte.

The porous body 130 b may be fixed by compressing respective frames 135of the first and second holders 130 a and 130 c against each otherexcluding the porous parts 136 thereof, or may be fixedly attached tothe frames 135 of the first and second holders 130 a and 130 c.

Terminals are formed on the frames 135 to be electrically connected tothe power supply 140.

Here, the porous body 130 b disposed between the first and secondholders 130 a and 130 c may be formed of a conductive metal fiber.

The conductive metal fiber is made of at least one metal selected fromstainless, copper, nickel and fecralloy. The metal selected is formedinto a metal fiber having a thickness of 1 to 100 μm utilizinghigh-vacuum melting and ultra rapid cooling disk, which are known in theart. This metal fiber may be formed in a web shape to allow pores to beformed uniformly.

Alternatively, the porous body 130 b may be formed of at least twolayers of web-shaped conductive metal fiber having a porosity gradientdifferent from each other.

The power supply 140 is electrically connected to the anode electrodeplate 131 and the cathode electrode plate 132 constituting the electrodepart 130 to supply current to the anode and cathode electrode plates 131and 132, respectively.

The power supply 140 may be electrically connected to the first andsecond holders 130 a and 130 c constituting the anode and cathodeelectrode plate 131 and 132, respectively, but not limited thereto. Thepower supply 140 may be electrically connected to the porous body 130 bdisposed between the first and second holders 130 a and 130 c.

When the electrolyte such as sea water is filled in the electrolyticbath 110 of the hydrogen generator 100 configured as above, theelectrode part 130 installed in the electrolytic bath 110 has most ofthe body portion immersed in the electrolyte.

Here, the cover 120 hermetically covers an open top of the electrolyticbath 110 and a sealer 115 is provided between an upper end of theelectrolytic bath 110 and the cover 120 so as to prevent the electrolytefrom being leaked to the outside.

In this state, when a switch (not shown) of the power supply 140electrically connected to the electrode part 130 is turned “on”, currentof a predetermined intensity is supplied to the anode electrode plate131 and cathode electrode plate 132 of electrode part 130, respectivelyto electrolyze the electrolyte of the electrolytic bath 110, therebygenerating hydrogen.

Here, each of the anode electrode plate 131 and cathode electrode plate132 immersed in the electrolyte of the electrolytic bath 110 includesthe first and second holders 130 a and 130 c each having the porous part136 formed thereon, and the porous body 130 b disposed between the firstand second holders 130 a and 130 c. Accordingly, the electrolyte freelypasses through the porous body 130 b made of a metal fiber through theporous parts 136, thereby increasing its contact area with the electrodepart over a case where the electrode plates are not configured as aporous structure. This as a result increases a contact area between theelectrolyte and the electrode plates to generate a higher amount ofhydrogen during electrolysis of the electrolyte.

That is, in a case where the anode electrode plate 131 is formed ofmagnesium (Mg) more ionizable than hydrogen, and the cathode electrodeplate 132 is formed of iron (Fe), when current is supplied to the anodeelectrode plate 131 and the cathode electrode plate 132, respectively,the magnesium of the anode electrode plate 131 reacts with water in theelectrolyte according to equations 1, 2 and 3, and then magnesiumhydroxide is generated in the electrolytic bath 100 to generate hydrogenaccording to equation 4.

Then, the hydrogen generated inside the electrolytic bath 110 isexhausted outward through the hydrogen outlet 124 formed in the cover120. The magnesium hydroxide remains in the electrolytic bath 110, andthe hydrogen exhausted outward is supplied to a power generator of afuel cell to generate electricity.

That is, the hydrogen is supplied to an anode through an anodeseparation plate provided in the power generator, and an air containingoxygen is supplied to a cathode through a cathode separation plateprovided in the power generator.

As described above, the hydrogen and air supplied to the power generatorflow, with a polyelectrolyte membrane interposed therebetween. In theanode, the hydrogen is electrochemically oxidized according to equation5 below and in the cathode, the oxygen is electrochemically reducedaccording to equation 6 below.

Here, electricity is generated due to migration of electrons created.The generated electricity is collected on anode and cathode collectionplates to be utilized as an energy source.

Anode electrode reaction: H₂->2H⁺+2e⁻  Equation 5

Cathode electrode reaction: (½)O₂+2H⁺+2e^(−-->H) ₂O   Equation 6

As set forth above, according to exemplary embodiments of the invention,an anode electrode plate and a cathode electrode plate immersed in anelectrolyte of an electrolytic bath are configured as a porous structureallowing the electrolyte to pass freely therethrough, thereby increasinga contact area between the electrode plates and the electrolyte. Thisincreases a surface area of an electrode part in contact with theelectrolyte within a limited space of the electrolytic bath to enable ahigher amount of hydrogen to be generated, while precluding a need forenlarging an inner space of the electrolytic bath or augmenting thenumber of the electrode plates disposed inside the electrolytic bath.

In addition, the hydrogen generator is less bulky and more compact, andcan be handled and used conveniently, thereby applicable to a fuel cellof e.g., a mobile terminal, an electronic notebook, a personal digitalassistant (PDA), a portable multimedia player (PMP), an MPEG audiolayer-III (MP3) player and a navigation.

While the present invention has been shown and described in connectionwith the exemplary embodiments, it will be apparent to those skilled inthe art that modifications and variations can be made without departingfrom the spirit and scope of the invention as defined by the appendedclaims.

1. A hydrogen generator having a porous electrode plate comprising: anelectrolytic bath having an electrolyte of a predetermined amount filledtherein; a cover hermetically covering an open top of the electrolyticbath and having at least one hydrogen outlet; an electrode part fixed tothe cover and having a porous structure formed on a body portion thereofto allow the electrolyte of the electrolytic bath to pass freelytherethrough, the body portion of the electrode part immersed in theelectrolytic bath; and a power supply supplying current to the electrodepart.
 2. The hydrogen generator of claim 1, wherein the electrode partcomprises an anode electrode plate and an anode electrode plate, whereineach of the anode and cathode electrode plates comprises: first andsecond holders each provided on a surface thereof with a porous partthrough which the electrolyte passes freely; and a porous body fixedlydisposed between the first and second holders.
 3. The hydrogen generatorof claim 2, wherein the porous body is formed of a conductive metalfiber.
 4. The hydrogen generator of claim 2, wherein the porous bodycomprises at least two layers of conductive metal fiber having aporosity gradient different from each other.
 5. The hydrogen generatorof claim 2, wherein the porous body is electrically connected to thepower supply.
 6. The hydrogen generator of claim 1, wherein a sealer isprovided between the electrolytic bath and the cover.